Formation and Description of Business - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Limited Partners' Capital Account [Line Items]
Limited partnership business formation date	Jan. 01, 1990
Portion of NPAMLP owned by limited partners	99.00%
Portion of NPAMLP owned by managing general and equity partners	1.00%
Future minimum rent	$ 4,260
Cash and cash equivalents	2,195	2,181	2,001	897
Line of credit facility remaining borrowing capacity	1,431
Wraparound mortgage payable	$ 126,666